Coarse salt and ground pepper
8 thin chicken cutlets (1 1/2 pounds total)
2 tablespoons Dijon mustard
1 package (10 ounces) frozen leaf spinach, thawed and squeezed dry
4 ounces Brie cheese, cut into 8 slices
1 cup orzo
2 plum tomatoes, cored and chopped
1/4 cup chopped fresh parsley
1 tablespoon butter
1 tablespoon fresh lemon juice
Set a large saucepan of salted water to boil. Heat broiler, with rack set 4 inches from heat. Place chicken on a large rimmed baking sheet lined with aluminum foil. Dividing evenly, spread one side of each cutlet with mustard; top with spinach, then cheese. Season with salt and pepper. Starting at short end, roll chicken up tightly, and arrange, seam side down, on sheet.
Season rolled chicken with salt and pepper. Broil, without turning, until tops are lightly browned and chicken is cooked through, 8 to 10 minutes.
Meanwhile, cook orzo in boiling water until al dente. Drain well; return to pot. Add tomatoes, parsley, butter, and lemon juice. Season with salt and pepper, and toss to combine. Serve stuffed chicken with orzo.